poor brake pressure

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Dec 18, 2020 | 09:02 AM

jimmy colon

Thread Starter

Heel & Toe

Joined: Dec 2020

Posts: 21

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From: port jefferson ny

poor brake pressure

was wondering do i need a master cylinder or booster? i have changed all the calipers recently. no matter how much i press i get no pressure. tried bleeding all of them all already. no leaks either. its an 82, i did recall i allways heard alittle clicking type noise when applying brakes before, i no longer hear that. any help to not start buying parts not needed

Dec 18, 2020 | 09:39 AM

The Grinch

Instructor

Joined: Feb 2017

Posts: 136

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From: Liberty Island

Did you run the master dry during the caliper change?

dis it have pressure then lose it during caliper bleeding?

Dec 18, 2020 | 10:52 AM

Sayfoo

Safety Car

Joined: Sep 2005

Posts: 4,229

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From: Orange County Ca

I just went through a similar problem.
Very hard pedal and no stopping power is probably the booster.
1st thing to do is to see if it holds vacuum.

Last edited by Sayfoo; Dec 18, 2020 at 12:55 PM.

Dec 19, 2020 | 10:47 AM

Idan55

Instructor

Joined: Mar 2018

Posts: 159

Likes: 18

From: FL

Quote:

Originally Posted by Sayfoo

I just went through a similar problem.
Very hard pedal and no stopping power is probably the booster.
1st thing to do is to see if it holds vacuum.

I have the exact same problem in my 82'. how did you check if it hold vacuum ?

Dec 19, 2020 | 11:05 AM

cagotzmann

Melting Slicks

Joined: Jun 2011

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Quote:

Originally Posted by Idan55

I have the exact same problem in my 82'. how did you check if it hold vacuum ?

You don't need to remove as shown in this picture. Just connect as shown. I try to see if it maintains the vacuum for at least 30 minutes without dropping at all. If it slowly drops over time its starting to fail, if it doesn't hold any vacuum it has failed.

Dec 19, 2020 | 11:14 AM

Idan55

Instructor

Joined: Mar 2018

Posts: 159

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From: FL

Quote:

Originally Posted by cagotzmann

how much psi it should hold? Where did you bought this vacuum gum from?

Dec 19, 2020 | 11:45 AM

Sayfoo

Safety Car

Joined: Sep 2005

Posts: 4,229

Likes: 643

From: Orange County Ca

Also, you can use engine vacuum--it's what's needed to work the brakes anyway. After running the engine and shutting it down, wait a bit--10 minutes--and pull the big hose off the booster. Do not touch the brake peddle during this time. If the booster and the check valve are working correctly, or the check valve is bad, nothing will happen. Then pull the check valve and you should hear a air woosh if the booster and check valve are good. If no air movement or noise, the booster is leaking.
You can check the check valve by sucking/blowing on it. Should only go 1 way.